Reichsacht

The imperial ban (German: Reichsacht) was a form of outlawry in the Holy Roman Empire. At different times, it could be declared by the Holy Roman Emperor, by the Imperial Diet, or by courts like the League of the Holy Court (Vehmgericht) or the Reichskammergericht.

People under imperial ban, known as Geächtete (from about the 17th century, colloquially also as Vogelfreierei, lit. "free as a bird"), lost all their rights and possessions. They were legally considered dead, and anyone was allowed to rob, injure or kill them without legal consequences. The imperial ban automatically followed the excommunication of a person, as well as extending to anyone offering help to a person under the imperial ban.

Those banned could reverse the ban by submitting to the legal authority. The Aberacht, a stronger version of the imperial ban, could not be reversed.

The imperial ban was sometimes imposed on whole Imperial Estates. In that case, other estates could attack and seek to conquer them. The effect of the ban on a city or other Estate was that it lost its Imperial immediacy and in the future would have a second overlord in addition to the emperor.

Famous people placed under the imperial ban included:

The imperial ban imposed by the Emperor Rudolf II on the city of Donauwörth after an anti-Catholic riot was one of the incidents leading to the Thirty Years' War.

...
Wikipedia